US9593935B2 - Optical image measuring apparatus - Google Patents

Optical image measuring apparatus Download PDF

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US9593935B2
US9593935B2 US14/795,289 US201514795289A US9593935B2 US 9593935 B2 US9593935 B2 US 9593935B2 US 201514795289 A US201514795289 A US 201514795289A US 9593935 B2 US9593935 B2 US 9593935B2
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image
interference
reference beam
objective lens
measurement target
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US20160054113A1 (en
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Kentaro Osawa
Naoko Senda
Daisuke Tomita
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Hitachi LG Data Storage Inc
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Hitachi LG Data Storage Inc
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/0209—Low-coherence interferometers
    • G01B9/02091—Tomographic interferometers, e.g. based on optical coherence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02056—Passive reduction of errors
    • G01B9/02058—Passive reduction of errors by particular optical compensation or alignment elements, e.g. dispersion compensation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02062—Active error reduction, i.e. varying with time
    • G01B9/02063—Active error reduction, i.e. varying with time by particular alignment of focus position, e.g. dynamic focussing in optical coherence tomography
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02075—Reduction or prevention of errors; Testing; Calibration of particular errors
    • G01B9/02078—Caused by ambiguity
    • G01B9/02079—Quadrature detection, i.e. detecting relatively phase-shifted signals
    • G01B9/02081—Quadrature detection, i.e. detecting relatively phase-shifted signals simultaneous quadrature detection, e.g. by spatial phase shifting
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02083—Interferometers characterised by particular signal processing and presentation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02083—Interferometers characterised by particular signal processing and presentation
    • G01B9/02087—Combining two or more images of the same region
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/02—Details
    • G01J3/0289—Field-of-view determination; Aiming or pointing of a spectrometer; Adjusting alignment; Encoding angular position; Size of measurement area; Position tracking
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00—Image enhancement or restoration
    • G06T5/50—Image enhancement or restoration using two or more images, e.g. averaging or subtraction
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/10—Image acquisition modality
    • G06T2207/10072—Tomographic images
    • G06T2207/10101—Optical tomography; Optical coherence tomography [OCT]
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00—Indexing scheme for image analysis or image enhancement
    • G06T2207/20—Special algorithmic details
    • G06T2207/20212—Image combination
    • G06T2207/20224—Image subtraction

Definitions

  • the present invention relates to an optical image measuring apparatus for observing a measurement target using interference of light beams.
  • OCT optical coherence tomography
  • a light beam from a light source is split into two: a signal beam to irradiate a measurement target and a reference beam to be reflected by a reference beam mirror without irradiating the measurement target. Then, the signal beam reflected by the measurement target is combined with and thus is caused to interfere with the reference beam, whereby an interference signal is obtained.
  • the OCT is broadly divided into the time domain OCT and the Fourier domain OCT depending on the method of moving the measurement position in the optical axis direction (hereinafter referred to as z-scan).
  • z-scan is performed by using a low coherence light source as a light source and moving a reference beam mirror during measurement. Accordingly, only the components in a signal beam that have the same optical path length as the reference beam interfere with the reference beam.
  • the obtained interference signal is subjected to envelope detection, a desired signal is obtained through demodulation.
  • the Fourier domain OCT is further divided into the wavelength-scanning OCT and the spectral domain OCT.
  • z-scan is performed by using a wavelength-scanning light source capable of causing the wavelength of an emitted beam to scan, and causing the wavelength to scan during measurement.
  • a wavelength-scanning light source capable of causing the wavelength of an emitted beam to scan, and causing the wavelength to scan during measurement.
  • a desired signal is obtained.
  • a broadband light source is used for a light source, and the following corresponds to the z-scan: splitting the generated interference beam using a beam splitter, and detecting the interference beam intensity (i.e., interference spectrum) for each wavelength component.
  • a desired signal is obtained.
  • reflected light from the inside of a measurement target is typically far weaker than reflected light from the surface of the measurement target and reflected light from the interface between the measurement target and a measurement target holding portion, such as cover glass or a cell culture vessel.
  • a measurement target holding portion such as cover glass or a cell culture vessel.
  • the refractive index of the culture solution is about 1.33
  • the reflectivity of the interface between the cell and the culture solution is about 0.022%.
  • the influence of reflected light from the interface between the measurement target and the measurement target holding portion appears in the xy image of the inside of the measurement target as an afterimage of the structure of the interface between the measurement target and the measurement target holding portion.
  • Such a method is considered to work in the conventional OCT in which the measurement position in the z direction is changed or moved by moving a reference beam mirror or sweeping the wavelength.
  • the conventional OCT uses an objective lens with low NA (typically, a NA of less than or equal to 0.1)
  • the xy resolution is about 20 to 30 ⁇ m.
  • the inventors studied a configuration in which a tomographic image of a measurement target is acquired by applying a laser light source with a long coherence length as a light source, causing a laser beam (i.e., signal beam) to be focused onto and irradiate the measurement target using an objective lens with high NA, and moving the objective lens to move the focus position.
  • a laser beam i.e., signal beam
  • An optical image measuring apparatus includes a light source configured to emit a laser beam; a beam splitter configured to split the laser beam emitted from the light source into a signal beam and a reference beam; a first objective lens configured to focus the signal beam onto a measurement target in a container to irradiate the measurement target with the signal beam; a focus position moving unit configured to move a focus position of the signal beam; a second objective lens configured to focus the reference beam; a reflecting mirror configured to reflect the reference beam that has passed through the second objective lens and return the reference beam to the second objective lens; a flat plate arranged between the second objective lens and the reflecting mirror; interference optics configured to combine the signal beam reflected or scattered by the measurement target with the reference beam that has been reflected by the reflecting mirror and has passed through the second objective lens, thereby generating three or more interference beams with different phases; and a photodetector configured to detect the interference beams.
  • the second objective lens is the same objective lens as the first objective lens
  • the flat plate has the same
  • the optical image measuring apparatus further includes an image generation unit configured to generate an image on the basis of a signal obtained from the photodetector for each focus position of the signal beam moved by the focus position moving unit, and an image processing unit configured to perform a subtraction process between two images generated by the image generation unit.
  • An optical image measuring method in accordance with the present invention is an optical image measuring method for splitting a laser beam into a signal beam and a reference beam, focusing the signal beam onto a measurement target to irradiate the measurement target with the signal beam, causing the signal beam reflected or scattered by the measurement target to interfere with the reference beam, thereby generating three or more interference beams with different phases, and acquiring a tomographic image of the measurement target on the basis of detection signals of the interference beams, the method including acquiring a first image on the basis of a detection signal obtained by moving a focus position of the signal beam in a direction perpendicular to an optical axis while using a plane wave as the reference beam; acquiring a second image on the basis of a detection signal obtained by moving the focus position of the signal beam in the direction perpendicular to the optical axis by providing a defocus aberration to the reference beam; and generating a third image by performing at least a subtraction process between the first image and the second image.
  • the step of generating the third image can be performed by subtracting the second image with adjusted luminance from the first image.
  • the amount of defocus aberration can be set such that, from one aspect, crosstalk that has appeared on the first image can be removed or reduced in the third image.
  • An optical image measuring apparatus in accordance with the present invention includes a light source configured to emit a laser beam; a beam splitter configured to split the laser beam emitted from the light source into a signal beam and a reference beam; an objective lens configured to focus the signal beam onto a measurement target to irradiate the measurement target with the signal beam; a focus position moving unit configured to move a focus position of the signal beam; a defocus aberration adjustment unit configured to adjust a defocus aberration of the reference beam; interference optics configured to combine the signal beam reflected or scattered by the measurement target with the reference beam, thereby generating three or more interference beams with different phases; a photodetector configured to detect the interference beams; an image generation unit configured to generate an image on the basis of output signals of the photodetector; and an image processing unit configured to apply image processing to the image generated by the image generation unit.
  • the third image is generated by subtracting the second image with adjusted luminance from the first image with the image processing unit.
  • the optical image measuring apparatus further includes a beam splitter configured to split the reference beam into a first reference beam and a second reference beam, the first reference beam not passing through the defocus aberration adjustment unit and the second reference beam passing through the defocus aberration adjustment unit; first interference optics and second interference optics as the interference optics.
  • the first interference optics are configured to generate interference beams of the signal beam reflected or scattered by the measurement target and the first reference beam.
  • the second interference optics are configured to generate interference beams of the signal beam reflected or scatted by the measurement target and the second reference beam.
  • An image generated by the image generation unit on the basis of output signals of a photodetector configured to detect the interference beams of the first interference optics is used as the first image
  • an image generated by the image generation unit on the basis of output signals of a photodetector configured to detect the interference beams of the second interference optics is used as the second image.
  • an optical image measuring apparatus can be provided that can suppress influence of strong reflected light generated from a specific reflecting surface, such as the surface of a measurement target, and thus can clearly visualize the structure of a region around the specific reflecting surface.
  • FIG. 1 is a schematic diagram showing an example of a measurement target of an OCT apparatus.
  • FIGS. 2A and 2B are schematic diagrams showing exemplary images obtained with the conventional OCT apparatus.
  • FIGS. 3A and 3B are schematic diagrams showing an exemplary configuration of the optical image measuring apparatus of the present invention.
  • FIG. 4 is a diagram showing exemplary operation procedures of the optical image measuring apparatus.
  • FIG. 5 is a schematic diagram showing an exemplary configuration of the optical image measuring apparatus of the present invention.
  • FIG. 6 is a diagram showing exemplary operation procedures of the optical image measuring apparatus of the present invention.
  • FIG. 7 is a schematic diagram showing another embodiment of an optical image measuring apparatus in accordance with the present invention.
  • FIGS. 8A and 8B are schematic diagrams of an image display unit.
  • a laser beam emitted from a light source is split into a signal beam and a reference beam, and the signal beam is focused onto a measurement target by an objective lens to irradiate the measurement target.
  • the focus position of the signal beam is moved by a focus position moving unit, and defocus of the reference beam is adjusted by a defocus aberration adjustment unit.
  • the signal beam reflected or scattered by the measurement target is combined with the reference beam by interference optics, whereby three or more interference beams with different phases are generated and detected.
  • An image generation unit generates image data on the basis of such detection signals, and an image processing unit performs image processing on the generated image.
  • the image processing unit on the basis of a first image obtained by not providing a defocus aberration to the reference beam with the defocus aberration adjustment unit and a second image obtained by providing a defocus aberration to the reference beam, generates a third image from which crosstalk components from a specific reflecting surface with high reflectivity, such as the surface of the measurement target, are removed.
  • the amount of defocus aberration provided to the reference beam by the defocus aberration adjustment unit is the same as that of reflected light components from the specific reflecting surface with high reflectivity contained in the signal beam.
  • the reflecting surface that generates high reflection is a reflecting surface with higher reflectivity than other portions of the measured region, and it is thus considered that reflected light from the reflecting surface obstructs clear visualization of the structure of the peripheral portion.
  • the reflecting surface is a surface for which a user can select removing the influence of reflected light therefrom.
  • the surface of the measurement target is irradiated with a signal beam through some container, the surface of the container is considered as the reflecting surface, or when the measurement target is contained in a liquid, such as a formalin solution, the liquid surface is considered as the reflecting surface.
  • the numerical aperture of the objective lens that focuses a signal beam onto the measurement target is set greater than or equal to 0.4.
  • interference beams are generated by the interference optics.
  • An interference phase of the signal beam and the reference beam of each of the four interference beams differs from one another by an integral multiple of approximately 90°, and a pair of interference beams, which have a difference of approximately 180° in the interference phase of the signal beam and the reference beam, is detected by a current differential photodetector.
  • the detector As a current differential detector is used, the detector will not be easily saturated even if the intensity of the reference beam is increased. Thus, the signal S/N ratio can be increased than when the current differential detector is not used.
  • an objective lens which is the same objective lens as the objective lens used for focusing the signal beam, a reflecting mirror, and an actuator, which changes the relative distance between the objective lens and the reflecting mirror, are used as the defocus aberration adjustment unit.
  • the reference beam with the same amount of defocus aberration as that of reflected light components from a specific reflecting surface with high reflectivity contained in the signal beam.
  • a laser beam emitted from a light source is split into a signal beam, a first reference beam, and a second reference beam, and the signal beam is focused onto a measurement target by an objective lens to irradiate the measurement target.
  • the focus position of the signal beam is moved by a focus position moving unit, and defocus of the second reference beam is adjusted by a defocus aberration adjustment unit.
  • the signal beam reflected or scattered by the measurement target is split into a first signal beam and a second signal beam.
  • the first signal beam and the first reference beam are combined by first interference optics, whereby three or more interference beams with different phases are generated and detected.
  • the second signal beam and the second reference beam are combined by second interference optics, whereby three or more interference beams with different phases are generated and detected.
  • An image generation unit generates image data on the basis of such detection signals, and an image processing unit performs image processing on the generated image.
  • the image processing unit on the basis of a first image obtained on the basis of the signals from the first interference optics and a second image obtained on the basis of the signals from the second interference optics, generates a third image in which crosstalk components from a specific reflecting surface with high reflectivity, such as the surface of the measurement target, are removed.
  • the amount of defocus aberration provided to the second reference beam by the defocus aberration adjustment unit is the same as that of reflected light components from the specific reflecting surface with high reflectivity contained in the signal beam.
  • the image (i.e., first image) and the image (i.e., second image) can be acquired under that conditions in which a defocus aberration is provided to the reference beam and a defocus aberration is not provided to the reference beam, respectively, through a single measurement, it is possible to suppress the influence of strong reflected light from a specific reflecting surface, such as the surface of the measurement target, in a shorter measurement time, and thus clearly visualize the structure of a region around the specific reflecting surface.
  • FIG. 3A is a schematic diagram showing an exemplary configuration of the optical image measuring apparatus of the present invention.
  • a single laser beam emitted from a light source 301 is converted into a collimated beam by a collimator lens 302 , and is subjected to polarization rotation by a ⁇ /2 plate 303 capable of adjusting the optical axis direction, and is further split into two: a signal beam and a reference beam by a light beam splitter including a polarization beam splitter 304 .
  • the signal beam passes through a ⁇ /4 plate 305 at which the optical axis is set to about 22.5° with respect to the horizontal direction, and thus is converted from the s-polarized beam into a circularly polarized beam.
  • the beam is focused onto a cultured cell 309 in a culture vessel 308 by an objective lens 306 with a numerical aperture of greater than or equal to 0.4, so as to irradiate the cultured cell 309 .
  • the objective lens 306 is designed to so that a spherical aberration becomes almost zero after a beam has passed through the bottom surface of the culture vessel 308 .
  • the objective lens 306 is moved by an objective lens actuator 307 , whereby the focus position (i.e., measurement position) of the signal beam is moved by the objective lens 306 .
  • the signal beam reflected or scattered by the measurement target passes through the objective lens 306 again, and is then converted from the circularly polarized beam into a p-polarized beam by the ⁇ /4 plate 305 . Then, the beam becomes incident on the polarization beam splitter 304 . Meanwhile, the reference beam is converted from the p-polarized beam into a circularly polarized beam by a ⁇ /4 plate 310 , and then becomes incident on a defocus aberration adjustment unit 315 arranged on the optical path of the reference beam.
  • the defocus aberration adjustment unit 315 includes an objective lens 311 , which is the same objective lens as the objective lens 306 , an objective lens actuator 312 , a flat plate 313 , which is formed of the same material as the culture vessel 308 and has the same thickness as the signal beam transmitting portion, that is, the bottom surface of the culture vessel 308 , and a reflecting mirror 314 .
  • a defocus aberration of the reference beam can be adjusted by changing the relative position between the objective lens 311 and the reflecting mirror with the objective lens actuator 312 .
  • the flat plate 313 is inserted to set the amount of spherical aberration of the reference beam to be equal to that of the signal beam.
  • the flat plate 313 is also changed correspondingly.
  • the reference beam that becomes incident on the defocus aberration adjustment unit 315 is focused by the objective lens 311 and is reflected by the reflecting mirror 314 after having passed through the flat plate 313 . Then, the beam passes through the flat plate 313 and the objective lens 311 again and is then converted from the circularly polarized beam into a s-polarized beam by the ⁇ /4 plate 310 . Then, the beam becomes incident on the polarization beam splitter 304 .
  • the signal beam and the reference beam are combined by the polarization beam splitter 304 , whereby a combined beam is generated.
  • the combined beam is guided to interference optics 323 that include a half beam splitter 316 , a ⁇ /2 plate 317 , a ⁇ /4 plate 318 , condenser lenses 319 and 320 , and Wollaston prisms 321 and 322 .
  • the combined beam that becomes incident on the interference optics 323 is divided into two: a transmitted beam and a reflected beam by the half beam splitter 316 .
  • the transmitted beam passes through the ⁇ /2 plate 317 at which the optical axis is set to about 22.5° with respect to the horizontal direction, and is focused by the condenser lens 319 , and is further split into two by the Wollaston prism 321 , whereby a first interference beam and a second interference beam having a phase difference of 180° are generated.
  • the first interference beam and the second interference beam are detected by a current differential photodetector 324 , whereby a differential output signal 336 that is proportional to the intensity difference between the first interference beam and the second interference beam is output.
  • the reflected beam passes through the ⁇ /4 plate 318 at which the optical axis is set to about 45° with respect to the horizontal direction, and is focused by the condenser lens 320 , and is further split into two by the Wollaston prism 322 , whereby a third interference beam and a fourth interference beam having a phase difference of about 180° are generated.
  • the third interference beam has a phase difference of about 90° from the first interference beam.
  • the third interference beam and the fourth interference beam are detected by a current differential photodetector 325 , whereby a differential output signal 327 that is proportional to the intensity difference between the third interference beam and the fourth interference beam is output.
  • the thus generated differential output signals 326 and 327 are input to an image generation unit 328 , whereby image data 329 is generated.
  • An image processing unit 330 generates new image data 331 on the basis of the image data 329 , and displays the data on the image display unit 332 .
  • FIG. 4 is a diagram showing exemplary operation procedures of the OCT apparatus in this embodiment.
  • an xz image of a measurement target that is, a tomographic image including an optical axis is acquired (S 11 ), and on the basis of the results, a user selects a reflecting surface position (z 0 ) at which strong reflected light, the influence of which should be removed, is generated (S 12 ).
  • the reflecting surface position (z 0 ) in this embodiment is the position of the interface between the culture vessel 308 and the cultured cell 309 .
  • the objective lens actuator 307 is driven so that the position of the signal beam focused by the objective lens 306 is two-dimensionally moved on a plane perpendicular to the optical axis.
  • the reference beam is a plane wave.
  • the objective lens actuator 312 of the defocus aberration adjustment unit 315 is driven to adjust the relative distance between the objective lens 311 and the reflecting mirror 314 so that the surface of the reflecting mirror 314 becomes the position at which the reference beam is focused by the objective lens 311 .
  • the defocus aberration is provided by displacing the focus position of the reference beam from the reflecting mirror 314 by z 0 -z m with the objective lens actuator 312 .
  • the xy image becomes almost the same as the image that remains as the afterimage in the first image.
  • the image processing unit 330 subtracts the second image with the adjusted luminance from the first image, thereby generating a third image with the removed afterimage (S 16 ), and displays the third image on the image display unit 332 (S 17 ).
  • the amount of defocus aberration that is provided to the reference beam by the defocus aberration adjustment unit 315 during acquisition of the second image in Step 15 can be considered as allowing the crosstalk components, which have appeared in the first image acquired in Step 14 , to be removed or reduced in the third image.
  • r represents the distance from the center of the optical axis
  • d represents the radius of the lens aperture
  • ⁇ represents the wavelength of the laser beam.
  • a ref and ⁇ ref represent the electric field amplitude and the phase of the reference beam, respectively, and ⁇ z ref represents the defocus amount of the reference beam (i.e., distance in the optical axis direction between the position of the reference beam focused by the objective lens 311 and the reflecting mirror 314 ).
  • W ⁇ z ref r 2 represents a defocus aberration provided to the reference beam by the defocus aberration adjustment unit 315 .
  • the Jones vector of the combined beam that has passed through the half beam splitter 316 and has further passed through the ⁇ /2 plate 317 is represented as follows.
  • the combined beam represent by equation (4) is split into p-polarized light components and s-polarized light components by the Wollaston prism 321 , which are then differentially detected by the current differential photodetector 324 , whereby a differential output signal 326 represented by the following equation is generated.
  • ⁇ represents the coordinate vector of the beam cross-section
  • D represents the detected region
  • ⁇ Dd ⁇ means an integration operation in the entire range in the beam.
  • the conversion efficiency of the detector is set to 1 for the sake of simplicity.
  • the Jones vector of the combined beam that has been reflected by the half beam splitter 316 and has further passed through the ⁇ /4 plate 318 is represented as follows.
  • the combined beam represented by equation (6) is split into p-polarized light components and s-polarized light components by the Wollaston prism 322 , which are then differentially detected by the current differential photodetector 325 , whereby a differential output signal 327 represented by the following equation is generated.
  • I ⁇ ( x , y ) ⁇ j ⁇ A ref ⁇ A sig , j ⁇ ( x , y ) ⁇ sin ⁇ ( k eff ⁇ ( z - z j - ⁇ ⁇ ⁇ z ref ) ) k eff ⁇ ( z - z j - ⁇ ⁇ ⁇ z ref ) ⁇ cos ⁇ ( k eff ⁇ ( z - z j - ⁇ ⁇ ⁇ z ref ) + ⁇ j ⁇ ( x , y ) ) ( 8 )
  • Q ⁇ ( x , y ) ⁇ j ⁇ A ref ⁇ A sig , j ⁇ ( x , y ) ⁇ sin ⁇ ( k eff ⁇ ( z - z j - ⁇ ⁇ ⁇ z ref ) ) k eff ⁇ ( z - z j - ⁇
  • the image generation unit 328 generates the image data 329 by performing the following operation on such signals.
  • Data( x,y ) ⁇ I ( x,y ) ⁇ 2 + ⁇ Q ( x,y ) ⁇ 2 (10)
  • equations (8) and (9) are approximately represented as follows.
  • the image data at this time is represented as follows.
  • the third term depends on the phases of the signal beam and the reference beam ( ⁇ m ⁇ 0 ).
  • the third term is considered to take a random value in each measurement due to random phase fluctuations resulting from disturbance.
  • the contribution of the third term can be significantly reduced by applying an averaging process a sufficient number of times.
  • phase fluctuations resulting from disturbance are small, the same advantageous effects are obtained by modulating the phase of the reference beam using a piezoelectric element and the like.
  • the first image data that is obtained by repeatedly performing measurement and an averaging process can be approximately represented as follows.
  • the image data at this time is represented by:
  • the first image and the second image are subjected to the following image processing by the image processing unit 330 , whereby third image data is generated.
  • g represents a known amount given by the following equation.
  • the spatial resolution in the optical axis direction is defined as the full width at half maximum of a peak, which corresponds to a single reflecting surface, obtained when the objective lens is moved in the z direction.
  • a signal that corresponds to equation (10) when there is only one reflecting surface is represented by the following equation.
  • the full width at half maximum of a signal from a single reflecting surface that is, spatial resolution in the optical axis direction can be approximately represented as follows.
  • ⁇ represents the wavelength of a laser beam and NA represents the numerical aperture of the objective lens 306 .
  • the wavelength of a light beam used by an OCT apparatus is typically about 600 to 1300 nm that are difficult to be absorbed by hemoglobin or even by water.
  • the numerical aperture of the objective lens is 0.4
  • spatial resolution in the optical axis direction at a wavelength of 600 to 1300 nm is about 3.3 to 7.2 ⁇ m
  • the plane resolution (about ⁇ /NA) is about 1.5 to 3.6 ⁇ m.
  • a pair of interference beams which have a difference of approximately 180° in the interference phase of a signal beam and a reference beam, is detected by a current differential photodetector.
  • the detector will not be easily saturated even if the intensity of the reference beam is increased, and the signal S/N ratio can thus be increased than when the current differential detector is not used.
  • the objective lens 311 that is the same objective lens as the objective lens 306 is used in the defocus aberration adjustment unit 315 , it is possible to easily provide the reference beam with the same amount of defocus aberration as that of reflected light from a specific reflecting surface with high reflectivity.
  • interference beams each having a phase difference of 90° are generated by the interference optics 323 and detected in this embodiment, the same advantageous effects as those in this embodiment can be obtained as long as the number of the interference beams is greater than or equal to three. For example, it is also possible to generate three interference beams each having a phase difference of 60°.
  • the averaging process is not an essential condition for obtaining the advantageous effects of the present invention. That is, the effect of suppressing crosstalk that is obtained by the averaging process and the effect of suppressing crosstalk in accordance with the present invention are independent.
  • FIG. 5 is a schematic diagram showing another embodiment of an optical image measuring apparatus in accordance with the present invention. It should be noted that components that are the same as those shown in FIG. 3 are denoted by the same reference numerals. Thus, some of the descriptions thereof are omitted.
  • This embodiment differs from Embodiment 1 in that an image acquired by using a plane wave as the reference beam and not providing a defocus aberration to the reference beam and an image acquired by providing a defocus aberration to the reference beam are obtained through a single measurement.
  • a laser beam emitted from the light source 301 is split into a signal beam and a reference beam by a polarization beam splitter.
  • the signal beam passes through the same optical path as that in Embodiment 1, and becomes incident on the polarization beam splitter 304 again.
  • the signal beam passes through the polarization beam splitter 304 , and is subjected to polarization rotation by about 45° by a ⁇ /2 plate 501 at which the optical axis is set to about 22.5° with respect to the horizontal direction, and is then split into p-polarized light components and s-polarized light components by a polarization beam splitter 502 , whereby a first signal beam and a second signal beam are generated.
  • the reference beam is reflected by a reflecting mirror 503 , and is subjected to polarization rotation by about 45° by a ⁇ /2 plate 504 at which the optical axis is set to about 22.5° with respect to the horizontal direction, and is then split into s-polarized light components and p-polarized light components by a polarization beam splitter 505 , whereby a first reference beam and a second reference beam are generated.
  • the first reference beam is reflected by the polarization beam splitter 505 , and then becomes incident on the polarization beam splitter 502 .
  • the second reference beam passes through the polarization beam splitter 505 , and is converted from the p-polarized beam into a circularly polarized beam by the ⁇ /4 plate 506 at which the optical axis is set to about 22.5° with respect to the horizontal direction. Then, the beam becomes incident on the ⁇ /4 plate 506 again after being reflected by a reflecting mirror 507 , and thus is converted from the circularly polarized beam into a s-polarized beam, and then becomes incident on the polarization beam splitter 505 .
  • the second reference beam is reflected by the polarization beam splitter 505 , and is converted from the s-polarized beam into a circularly polarized beam by a ⁇ /4 plate 508 at which the optical axis is set to about 22.5° with respect to the horizontal direction. Then, the beam is provided with a defocus aberration by the defocus aberration adjustment unit 315 , and becomes incident on the ⁇ /4 plate 508 again to be converted from the circularly polarized beam into a p-polarized beam, and further passes through the polarization beam splitter 505 and becomes incident on the polarization beam splitter 502 .
  • the first signal beam and the first reference beam are combined by the polarization beam splitter 502 , whereby a first combined beam is generated.
  • the second signal beam and the second reference beam are combined by the polarization beam splitter 502 , whereby a second combined beam is generated.
  • the first combined beam is guided to first interference optics 323 a that include a half beam splitter 316 a , a ⁇ /2 plate 317 a , a ⁇ /4 plate 318 a , condenser lenses 319 a and 320 a , and Wollaston prisms 321 a and 322 a .
  • the second combined beam is guided to second interference optics 323 b that include a half beam splitter 316 b , a ⁇ /2 plate 317 b , a ⁇ /4 plate 318 b , condenser lenses 319 b and 320 b , and Wollaston prisms 321 b and 322 b .
  • the function of each of the first interference optics 323 a and the second interference optics 323 b is the same as that of the interference optics 323 in Embodiment 1. Thus, the description thereof is omitted herein.
  • Differential output signals 326 a and 327 a that are generated by detecting interference beams generated by the first interference optics 323 a are input to the image generation unit 328 , whereby image data corresponding to the image represented by equation (14) in Embodiment 1 is generated.
  • differential output signals 326 b and 327 b that are generated by detecting interference beams generated by the second interference optics 323 b are input to the image generation unit 328 , whereby image data corresponding to the image represented by equation (18) in Embodiment 1 is generated.
  • FIG. 6 is a diagram showing exemplary operation procedures of the optical image measuring apparatus of the present invention.
  • the device configuration is the same as that in Embodiment 1 shown in FIG. 3 , the description thereof is omitted.
  • This embodiment differs from Embodiment 1 in that crosstalk due to reflected light from a plurality of positions z is suppressed.
  • n reflecting surfaces that can be selected by a user to remove the influence of reflected light therefrom, and the n reflecting surfaces are S 1 , . . . , S n -th reflecting surfaces counted from the surface.
  • the image processing unit 330 subtracts the second image group with adjusted luminance from the first image, thereby generating a third image with the removed afterimage (S 26 ), and causes the image display unit 332 to display the image (S 27 ).
  • the first image data which is obtained by acquiring image data generated on the basis of the detection signals represented by equations (23) and (24) a plurality of times and averaging them, is approximately represented by the following equation.
  • the third image data represented by equation (29) is an image in which crosstalk components from a plurality of reflecting surfaces is suppressed.
  • this embodiment it is possible to, by subtracting a plurality of images (i.e., second image group) acquired by providing a predetermined amount of defocus aberration to the reference beam, the luminance of which is adjusted at a predetermined magnification, from an image (i.e., first image) acquired by not providing a defocus aberration to the reference beam, obtain an image from which crosstalk due to not only reflected light from a single specific reflecting surface but also reflected light from a plurality of reflecting surfaces, which are selected by a user, is removed. Accordingly, it is possible to more clearly visualize a region around the specific reflecting surface from which strong reflection is generated.
  • FIG. 7 is a schematic diagram showing another embodiment of an optical image measuring apparatus in accordance with the present invention.
  • components that are the same as those shown in FIG. 3 are denoted by the same reference numerals. Thus, some of the descriptions thereof are omitted.
  • a case is supposed where a measurement target holding portion like a culture vessel for holding a measurement target is not necessary, or a case a measurement target holding portion is difficult to be provided.
  • a signal beam in this embodiment does not irradiate the measurement target through a culture vessel unlike in Embodiment 1 but directly irradiates the measurement target 309 .
  • the flat plate 313 is removed from the defocus aberration adjustment unit 315 .
  • This embodiment differs from Embodiment 1 in this point.
  • the image processing method performed by the image processing unit 330 differs from that in Embodiment 1.
  • the operation methods other than the image processing method are the same as those in Embodiment 1. Thus, herein, only the image processing method performed by the image processing unit 330 will be described.
  • the image processing unit 330 generates the third image data by performing the following operation on the first and second image data.
  • G represents a given constant that can be freely set by a user, and the initial value thereof is set to g given by equation (20).
  • FIG. 8A is a schematic diagram of the image display unit 332 at this time.
  • the image display unit 332 displays the third image and the value of G at that time.
  • the user is able to freely set the value of G on the screen using a keyboard, a mouse, or the like.
  • the value of G is changed to a given value that is determined to be optimal by the user.
  • the changed value of G is transmitted to the image processing unit 330 , so that the third image data is generated again and is displayed on the image display unit 332 .
  • FIG. 8B shows a schematic diagram of the image display unit 332 at this time.
  • the user is able to freely set the value of G in equation (31).
  • the present invention is not limited to the aforementioned embodiments, and includes a variety of variations.
  • the present invention need not include all of the configurations described in the embodiments. It is possible to replace a part of a configuration of an embodiment with a configuration of another embodiment.

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Publication number Priority date Publication date Assignee Title
JP6462432B2 (ja) * 2015-03-11 2019-01-30 株式会社日立エルジーデータストレージ 光計測装置及び光計測方法
JP5979567B1 (ja) * 2015-04-30 2016-08-24 パナソニックＩｐマネジメント株式会社 植物ストレス検出装置及び植物ストレス検出方法
JP6765786B2 (ja) * 2015-05-01 2020-10-07 キヤノン株式会社 撮像装置、撮像装置の作動方法、情報処理装置、及び情報処理装置の作動方法
FR3050038B1 (fr) * 2016-04-06 2018-05-18 Lltech Management Procede et dispositif de microscopie interferentielle plein champ en lumiere incoherente
JP6666792B2 (ja) * 2016-05-20 2020-03-18 株式会社日立エルジーデータストレージ 光画像計測装置、光画像計測方法
JP6728007B2 (ja) * 2016-09-23 2020-07-22 株式会社Ｓｃｒｅｅｎホールディングス 撮像装置および撮像方法
JP6720051B2 (ja) 2016-10-27 2020-07-08 株式会社日立エルジーデータストレージ 光画像計測装置、光画像計測方法
US10323926B2 (en) * 2017-06-21 2019-06-18 Canon U.S.A., Inc. Crosstalk elimination or mitigation in optical coherence tomography
JP7000176B2 (ja) * 2018-01-30 2022-01-19 株式会社日立ハイテク 光画像計測装置
JP7174604B2 (ja) * 2018-11-28 2022-11-17 株式会社日立ハイテク 光画像計測装置、光画像計測方法
EP4266693A4 (en) * 2021-07-06 2024-07-17 Samsung Electronics Co Ltd ELECTRONIC IMAGE PROCESSING DEVICE AND OPERATING METHOD THEREFOR

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070238955A1 (en) * 2006-01-18 2007-10-11 The General Hospital Corporation Systems and methods for generating data using one or more endoscopic microscopy techniques
US20090296542A1 (en) * 2008-05-30 2009-12-03 Sony Corporation Optical disc appartus and correction servo control signal generation method
US20100195876A1 (en) * 2007-05-04 2010-08-05 Universitat Politecnica De Catalunya System and method for measuring light scattering in the eyeball or eye region by recording and processing retinal images
US20110310395A1 (en) * 2010-06-18 2011-12-22 National Taiwan University Three-dimensional optical coherence tomography confocal imaging apparatus
US20120300217A1 (en) 2010-03-25 2012-11-29 Canon Kabushiki Kaisha Optical tomographic imaging apparatus
US20130120614A1 (en) * 2011-03-23 2013-05-16 Ichiro Oyama Image processing device, imaging device, and image processing method
US20140029405A1 (en) * 2012-07-30 2014-01-30 Hitachi Consumer Electronics Co., Ltd. Optical information reproduction apparatus
US20140204388A1 (en) 2013-01-24 2014-07-24 Hitachi Media Electronics Co., Ltd. Optical measuring apparatus

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4517211B2 (ja) * 2000-05-12 2010-08-04 株式会社トプコン 眼特性測定装置
FR2960291B1 (fr) * 2010-05-18 2015-04-03 Lltech Man Methode et dispositif de microscopie interferentielle plein champ a haute resolution
JP6053138B2 (ja) * 2013-01-24 2016-12-27 株式会社日立エルジーデータストレージ 光断層観察装置及び光断層観察方法

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070238955A1 (en) * 2006-01-18 2007-10-11 The General Hospital Corporation Systems and methods for generating data using one or more endoscopic microscopy techniques
US20100195876A1 (en) * 2007-05-04 2010-08-05 Universitat Politecnica De Catalunya System and method for measuring light scattering in the eyeball or eye region by recording and processing retinal images
US20090296542A1 (en) * 2008-05-30 2009-12-03 Sony Corporation Optical disc appartus and correction servo control signal generation method
US20120300217A1 (en) 2010-03-25 2012-11-29 Canon Kabushiki Kaisha Optical tomographic imaging apparatus
US20110310395A1 (en) * 2010-06-18 2011-12-22 National Taiwan University Three-dimensional optical coherence tomography confocal imaging apparatus
US20130120614A1 (en) * 2011-03-23 2013-05-16 Ichiro Oyama Image processing device, imaging device, and image processing method
US20140029405A1 (en) * 2012-07-30 2014-01-30 Hitachi Consumer Electronics Co., Ltd. Optical information reproduction apparatus
US20140204388A1 (en) 2013-01-24 2014-07-24 Hitachi Media Electronics Co., Ltd. Optical measuring apparatus

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
Binding, J. et al., "Brain Refractive Index Measured in Vivo with High-NA Defocus-Corrected Full-Field OCT and Consequences for Two-Photon Microscopy", Optics Express, Mar. 14, 2011, pp. 4833-4847, vol. 19, No. 6.
Extended European Search Report received in corresponding European Application No. 15001829.9 dated Jan. 13, 2016.
Labiau, S. et al., "Defocus Test and Defocus Correction in Full-Field Optical Coherence Tomography", Optics Letters, May 15, 2009, pp. 1576-1578, vol. 34, No. 10.
Subhash, H. M., "Full-Field and Single-Shot Full-Field Optical Coherence Tomography: A Novel Technique for Biomedical Imaging Applications", Advances in Optical Technologies, Jan. 1, 2012, pp. 205-226, vol. 1315, No. 3.

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